1. Field of the Invention
The present invention relates to a motor suitable for closed type electric compressors. The present application is based on Japanese Patent Application No. Hei 9-187221, the contents of which are herein incorporated by reference.
2. Related Art
One embodiment of conventional closed type electric compressors is shown in FIGS. 3 and 4.
A rotary compression mechanism 3 and a motor 100 for driving it through a crank shaft 4 are housed in a closed casing 1.
A stator 101 of the motor 100 is fixed by forcibly pressing it into the casing 1 and a rotor 102 is fixed to the upper part of the crank shaft 4.
The rotary compression mechanism 3 comprises a rolling piston 6 relatively rotatably fitted to a crank pin 5 of the crank shaft 4, a cylinder block 7 fixed to the casing 1 by welding, an upper bearing 8 for closing off an upper opening of the cylinder block 7, a lower bearing 9 for closing off a lower opening of the cylinder block 7, a blade 10 supported retractably in a slot 21 formed in the cylinder block 7, and a press spring 11 positioned behind the blade 10 for pressing the blade 10.
The crank shaft 4 is journaled in the upper bearing 8 and the lower bearing 9.
The rolling piston 6 is accommodated in a cylinder chamber 12 defined by the cylinder block 7, the upper bearing 8, and the lower bearing 9 and by abutting the tip of the blade 10 against the outer circumferential surface of the rolling piston 6, a suction chamber 13 is defined on one side of the blade 10 and a compression chamber 14 is defined on the other side.
When the crank shaft 4 is driven rotatably by the motor 100, the rolling piston 6 is rotatably moved eccentrically in the direction of the arrow in the cylinder chamber 12 and simultaneously therewith a gas is sucked into a suction chamber 13 through a suction pipe 20 and the gas in the compression chamber 14 is compressed.
The compressed gas is passed through a discharge port 22 formed in the upper bearing 8 to push up a discharge valve (not shown) and is introduced into a discharge muffler chamber 27 defined by the upper surface of the upper bearing 8 and a cover 26 covering it, where the pulsating component is removed.
Then, the gas enters, through a hole (not shown) formed in the cover 26, a first expansion chamber 28 defined below the motor 100, where it is expanded and the pulsating component is further removed.
Then the gas enters, through an air gap between the stator 101 and the rotor 102 and gas passages 29 formed between the stator 101 and the casing 1, a second expansion chamber 15 defined above the motor 100, where it is expanded and the pulsating component is further removed, and thereafter it is released into the outside through a discharge pipe 16.
A lubricating oil 17 is reserved in the bottom section in the casing 1 and is pumped up by a centrifugal oil pump 18 built in the crank shaft 4 to lubricate, for example, the sliding surfaces of the crank shaft 4, the upper bearing 8, and the lower bearing 9, the sliding surfaces of the crank pin 5 and the rolling piston 6, and the sliding surfaces of the rolling piston 6 and the cylinder 7 through a lubricating passage 19 formed in the crank shaft 4.
FIG. 5 is a transverse sectional view of the motor 100.
The rotor 102 is provided with a cylindrical core 111 comprising a plurality of layered laminations 110 that are composed of thin silicon steel sheets having the same size and the same shape, and a plurality of permanent magnets 115 are equi-spaced and embedded circumferentially along the outer circumference of the core 111.
The stator 101 is provided with laminations 104 composed of a plurality of thin silicon steel sheets having the same size and the same shape, and the laminations 104 are layered one on top of the other aligned with recesses 109 for auto-clamping, and are integrated by caulking to constitute a cylindrical core 105.
A plurality of slots 106 that have the same size and the same shape and are equi-spaced are formed circumferentially along the inner circumference of each lamination 104.
The outer periphery of each lamination 104 is formed with recesses 107 for the formation of the gas passages 29 and recesses 108 with which jigs for positioning will be engaged when the laminations 104 are layered and united together.
A plurality of windings 112 each covered with insulating paper 113 are passed through each slot 106 when the windings 112 are wound for the core 105.
When the stator 101 is forced into the casing 1, large-diameter sections 103 of each lamination 104 come in contact with the inner surface of the casing 1 and the recesses 107 and the inner surface of the casing 1 define the gas passages 29.
In the conventional motor 100, since the slots 106 formed in the laminations 104 of the stator 101 are the same in shape and size, the distance between the outer circumferential ends of the slots 106 positioned circumferentially inside of the recesses 107 and the recesses 108 that are small-diameter sections and the outer peripheries of the laminations 104, that is, the yoke length L, is shorter than that of the large-diameter sections 103, and therefore there is a problem that when electricity is passed to the windings 112, the magnetic flux passing through the yoke length L is decreased and hence the performance of the motor 100 is lowered.